I was using "Kelvin" in the context of growing plants, where the term is essentially synonymous with "color temperature". In the past, a Kelvin of 5000 to 6500 degrees was considered best for most aquatic plants. The sun at the equator approximates that. Are we saying that doesn't matter with LED's?

To restate my question about light and tank depth, how does one determine how many LED's a tank a tank needs?

It would seen that a deep tank would need more light that a shallower one. Some fixtures contain more LED's than others with the same dimensions and they'd then seem to produce more light at the bottom of the tank, but do they?